Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface

Vibration dependent branching and photoelectron angular distributions observed across the Cooper minimum region of bromobenzene

Vibrational state-resolved photoelectron anisotropy parameters, beta, for the ~X 2B1, ~B 2B2, and ~C2B1 state ionizations of bromobenzene have been recorded at photon energies ranging from 20.5 to 94 eV, so spanning the region of the expected bromine Cooper minimum (CM). The ~X state displays no CM and its beta value is also independent of vibrational level, in accord with the Franck-Condon Approximation. The ~B and ~ C state beta values display the CM to differing degrees, but both show a vibrational dependence that extends well below the obvious CM dip. Calculations are presented that replicate these observations of Franck-Condon Approximation breakdown spanning an extended photon energy range. This is the first demonstration of such wide-ranging breakdown detected in the beta anisotropy parameter in the absence of any resonance. Measured and calculated vibrational branching ratios for these states are also presented. Although the ~B state branching ratios remain constant, in accord with Franck-Condon expectations, the ~X and (especially) the ~C state ratios display weak, quasi-linear variations across the studied range of photon energy, but with no apparent correlation with the CM position

Spatial structure of the 8200 cal yr BP event in northern Europe

International audienceA synthesis of well-dated high-resolution pollen records suggests a spatial structure in the 8200 cal yr BP event in northern Europe. The temperate, thermophilous tree taxa, especially Corylus, Ulmus, and Alnus, decline abruptly between 8300 and 8000 cal yr BP at most sites located south of 61° N, whereas there is no clear change in pollen values at the sites located in the North-European tree-line region. Pollen-based quantitative temperature reconstructions and several other, independent palaeoclimate proxies, such as lacustrine oxygen-isotope records, reflect the same pattern, with no detectable cooling in the sub-arctic region. The observed patterns challenges the general view of the wide-spread occurrence of the 8200 cal yr BP event in the North Atlantic region. An alternative explanation is that the cooling during the 8200 cal yr BP event took place mostly during the winter and spring, and the ecosystems in the south responded sensitively to the cooling during the onset of the growing season. In contrast, in the sub-arctic area, where the vegetation was still dormant and lakes ice-covered, the cold event is not reflected in pollen-based or lake-sediment-based records

X-ray induced fragmentation of size-selected salt cluster-ions stored in an ion trap

Peer reviewe

A novel, high conductance channel of mitochondria linked to apoptosis in mammalian cells and Bax expression in yeast

During apoptosis, proapoptotic factors are released from mitochondria by as yet undefined mechanisms. Patch-clamping of mitochondria and proteoliposomes formed from mitochondrial outer membranes of mammalian (FL5.12) cells has uncovered a novel ion channel whose activity correlates with onset of apoptosis. The pore diameter inferred from the largest conductance state of this channel is ∼4 nm, sufficient to allow diffusion of cytochrome c and even larger proteins. The activity of the channel is affected by Bcl-2 family proteins in a manner consistent with their pro- or antiapoptotic properties. Thus, the channel activity correlates with presence of proapoptotic Bax in the mitochondrial outer membrane and is absent in mitochondria from cells overexpressing antiapoptotic Bcl-2. Also, a similar channel activity is found in mitochondrial outer membranes of yeast expressing human Bax. These findings implicate this channel, named mitochondrial apoptosis–induced channel, as a candidate for the outer-membrane pore through which cytochrome c and possibly other factors exit mitochondria during apoptosis

Characterization of Novel Cutaneous Human Papillomavirus Genotypes HPV-150 and HPV-151

DNA from two novel HPV genotypes, HPV-150 and HPV-151, isolated from hair follicles of immuno-competent individuals, was fully cloned, sequenced and characterized. The complete genomes of HPV-150 and HPV-151 are 7,436-bp and 7,386-bp in length, respectively. Both contain genes for at least six proteins, namely E6, E7, E1, E2, L2, L1, as well as a non-coding upstream regulatory region located between the L1 and E6 genes: spanning 416-bp in HPV-150 (genomic positions 7,371 to 350) and 322-bp in HPV-151 (genomic positions 7,213 to 148). HPV-150 and HPV-151 are phylogenetically placed within the Betapapillomavirus genus and are most closely related to HPV-96 and HPV-22, respectively. As in other members of this genus, the intergenic E2-L2 region is very short and does not encode for an E5 gene. Both genotypes contain typical zinc binding domains in their E6 and E7 proteins, but HPV-151 lacks the regular pRb-binding core sequence within its E7 protein. In order to assess the tissue predilection and clinical significance of the novel genotypes, quantitative type-specific real-time PCR assays were developed. The 95% detection limits of the HPV-150 and HPV-151 assays were 7.3 copies/reaction (range 5.6 to 11.4) and 3.4 copies/reaction (range 2.5 to 6.0), respectively. Testing of a representative collection of HPV-associated mucosal and cutaneous benign and malignant neoplasms and hair follicles (total of 540 samples) revealed that HPV-150 and HPV-151 are relatively rare genotypes with a cutaneous tropism. Both genotypes were found in sporadic cases of common warts and SCC and BCC of the skin as single or multiple infections usually with low viral loads. HPV-150 can establish persistent infection of hair follicles in immuno-competent individuals. A partial L1 sequence of a putative novel HPV genotype, related to HPV-150, was identified in a squamous cell carcinoma of the skin obtained from a 64-year old immuno-compromised male patient

Bim and Bmf synergize to induce apoptosis in Neisseria gonorrhoeae infection

Abstract: Bcl-2 family proteins including the pro-apoptotic BH3-only proteins are central regulators of apoptotic cell death. Here we show by a focused siRNA miniscreen that the synergistic action of the BH3-only proteins Bim and Bmf is required for apoptosis induced by infection with Neisseria gonorrhoeae (Ngo). While Bim and Bmf were associated with the cytoskeleton of healthy cells, they both were released upon Ngo infection. Loss of Bim and Bmf from the cytoskeleton fraction required the activation of Jun-N-terminal kinase-1 (JNK-1), which in turn depended on Rac-1. Depletion and inhibition of Rac-1, JNK-1, Bim, or Bmf prevented the activation of Bak and Bax and the subsequent activation of caspases. Apoptosis could be reconstituted in Bim-depleted and Bmf-depleted cells by additional silencing of antiapoptotic Mcl-1 and Bcl-XL, respectively. Our data indicate a synergistic role for both cytoskeletal-associated BH3-only proteins, Bim, and Bmf, in an apoptotic pathway leading to the clearance of Ngo-infected cells. Author Summary: A variety of physiological death signals, as well as pathological insults, trigger apoptosis, a genetically programmed form of cell death. Pathogens often induce host cell apoptosis to establish a successful infection. Neisseria gonorrhoeae (Ngo), the etiological agent of the sexually transmitted disease gonorrhoea, is a highly adapted obligate human-specific pathogen and has been shown to induce apoptosis in infected cells. Here we unveil the molecular mechanisms leading to apoptosis of infected cells. We show that Ngo-mediated apoptosis requires a special subset of proapoptotic proteins from the group of BH3-only proteins. BH3-only proteins act as stress sensors to translate toxic environmental signals to the initiation of apoptosis. In a siRNA-based miniscreen, we found Bim and Bmf, BH3-only proteins associated with the cytoskeleton, necessary to induce host cell apoptosis upon infection. Bim and Bmf inactivated different inhibitors of apoptosis and thereby induced cell death in response to infection. Our data unveil a novel pathway of infection-induced apoptosis that enhances our understanding of the mechanism by which BH3-only proteins control apoptotic cell death